The present invention relates to an electro-optical light modulating device and to methods of its fabrication. More particularly, the present invention relates to an electro-optical device which can be used to display an image by controllably changing its optical behavior at selected locations under the influence of a magnetic or electric flux or field.
As used herein throughout the term "image" refers to any pictorial, graphic and/or alphanumeric information.
As used herein throughout the verb "display" refers to a visual presentation of any type and in any context.
Electro-optical light modulating devices are structures designed to change their optical behavior in response to an applied electric or magnetic flux or field, e.g., electric potential, voltage or current. As such, electro-optical light modulating devices include an electro-optically active substance which is capable of reversibly changing its optical behavior when subjected to an electric or magnetic flux or field and an electric or magnetic flux or field generator for generating the flux or field. As further detailed hereinunder, a careful design achieved by "high precision methods" enables the application of an electric or magnetic flux or field at desired spatial locations, so as to form images.
As used herein throughout, the term "substance" refers to any compound, composition, dispersion, suspension or mixture in a solid, gel or fluid state.
Electro-optically active substances can be broken into electrochromic light modulating substances and electrophoretic light modulating substances.
Electrochromic light modulating substances include a variety of chemicals and polymers being capable of reversibly changing their color and/or their optical density as a response to electrochemical oxidation-reduction reactions. An example for the use of an electrochromic light modulating substance in an electro-optical light modulating device is disclosed in U.S. Pat. No. 5,585,958, which is incorporated by reference as if fully set forth herein.
Electrophoretic light modulating substances are suspensions including colored or opaque particles (e.g., beads) carrying a magnetic or electric charge and a fluid for suspending these particles. Being charged, the particles are capable of reversibly and controllably changing their disposition as a response to an applied magnetic or electric flux or field by executing a movements, e.g., a linear and/or rotational movement. Examples for the use of electrophoretic light modulating substances in electro-optical light modulating devices are disclosed in U.S. Pat. Nos. 5,057,363; 4,211,668; and 3,383,382, which are incorporated by reference as if fully set forth herein. In these cases, magnetically or electrostatically charged particles suspended in a dielectric fluid are used and are capable of changing the optical behavior of the suspension under the influence of a magnetic or an electric flux or field.
Be it electrochromic or electrophoretic light modulating substance based electro-optical light modulating device, all electro-optical light modulating devices include a magnetic or electric flux or field generator. The generator typically includes at least a pair of electrodes, of which at least one is formed as a dense pattern (e.g., a set of lines or a grid) applied to a rigid, planar and continuous substrate by microphotolithography, multilayer screen printing or by any other technique of high precision. A second electrode employed is typically transparent and is made of a thin electroconductive film, typically deposited over a transparent insulating substrate electrically separating the electrodes. The electro-optical light modulating substance is positioned as a layer in between the electrodes.
As a result, prior art electro-optical light modulating devices are limited in their dimensions, in their flexibility and in their foldability. In addition, the manufacturing process of such prior art electro-optical light modulating devices is complicated and cost-ineffective.
There is thus a widely recognized need for, and it would be highly advantageous to have, an electro-optical light modulating device devoid of the above limitations, which device is (i) readily fabricated in any desired dimensions; (ii) flexible; (iii) foldable/collapsible; (iv) simple to manufacture; and therefore (v) cost-effective.